Polyphenyl ether lubricating compositions

ABSTRACT

COMPOSITION COMPRISING POLYPHENYL ETHERS OR MIXTURES THEREOF AND PERFLUORO ALIPHATIC DIBASIC ACIDS EXHIBIT IMPROVED LUBRICATING PROPERTIES OVER WIDE TEMPERATURE RANGES.

United States Patent US. Cl. 25254.6 5 Claims ABSTRACT OF THE DISCLOSUREComposition comprising polyphenyl ethers or mixtures thereof andperfluoro aliphatic dibasic acids exhibit improved lubricatingproperties over wide temperature ranges.

This invention relates to improved lubricating compositions comprisingpolyphenyl ethers and mixtures thereof containing from 3 to 8 aromaticgroups and a perfiuoro aliphatic dibasic acid as a lubricating additive.

Polyphenyl ethers have found wide application as functional fluids inview of their excellent thermal stability and lubricity. For examplethey have been found to be valuable as hydraulic fluids and aslubricants in motor operation, particularly in jet engines.

Development of synthetic base stocks such as the polyphenyl ether hasprovided lubricant fluids which are useful at elevated temperature suchas 400 to 500 F. It is known that one of the aspects in which thepolyphenyl ether base stocks are considered deficient is in theirlubricating characteristics. These lubricating characteristics includethe load-carrying abilities and wear properties, especially underconditions of high pressures and temperatures reached in the advancedesign aircraft engines. Thus there is a demand for polyphenyl ethershaving improved lubricity properties.

An object of the present invention is to provide base stock compositionsemploying polyphenyl ethers or mixtures thereof that exhibit improvedlubricating properties.

These and other objects will become evident upon consideration of thefollowing specification and example.

It has now been found that compositions comprising a major amount of apolyphenyl ether base stock and a lubricating additive amount of aperfluorinated aliphatic dibasic acid, have unusual ability to lubricateunder high load at high temperatures.

Any of the well known polyphenyl ether base stocks can be used inaccordance with this invention. However, the polyphenylether base stocksrepresented by a member selected from the following formulae arepreferred.

where m is 2, 3, or 4 such as ice 2 Q such as 3,3'-bisphenoxy biphenyl oo H MM 23 such as 1,3,4-triphenoxybenzene and mixtures thereof.

Mixtures of polyphenyl ethers in which the nonterminal phenylene ringsare linked through oxygen atoms in the meta and/or parapositions, havebeen found to be particularly suitable. An example of such polyphenylether compositions are those containing, in percent by weight, fromabout 0 to 6% of o-bis(m-phenoxyphenoxy)benzene (1), about 40 to 85% ofm-bis(m-phenoxyphenoxy)- benzene (2), about 0 to 40% ofm-[(m-phenoxyphenoxy) (p-phenoxyphenoxy)]benzene (3), about 0 to 12% ofp-bis(m-phenoxyphenoxy)benzene (4), about 0 to 10% of p-[(p-phenoxyphenoxy) (m-phenoxyphenoxy) ]benzene (5), and about 0 to 6% ofm-bis(p-phenoxyphenoxy) benzene (6). Typical compositions of suchmixtures are listed below. The number in parentheses refers to thecompound mentioned above having the same number thereafter.

Mixtures percent by weight of components A B C D Component:

wherein n is an integer of from 1 to 6. It is particularly preferred toemploy perfluorinated dibasic acids of Formula V wherein n is an integerof from 2 to 4.

Illustrative of the perfluorinated dibasic acids represented by FormulaV are, for example, perfluoro malonic acid, perfluoro succinic acid,perfluoroglutaric acid, perfiuoro adipic acid,-perfluoropimelic acid,and perfluoro suberic acid.

The improvement in lubricity characteristics achieved by the addition ofthe perfluoro aliphatic dibasic acid to the polyphenyl ether base fluidis unusualaud surprising. The compositions are particularly useful forsteel on steel lubrication.

The compositions of this invention contain a major amount of thepolyphenyl ether base stock, i.e., at least 50% by weight of the totalcomposition comprises a polyphenyl ether. It is preferred that at least60% by weight of the composition be a polyphenyl ether base stock andeven more preferred that at least 85% by weight of the total compositioncomprise a polyphenyl ether.

The compositions of this invention can also contain from 0.01 to byweight of the total composition of a dialkyl hydrogen phosphite extremepressure additive. The dialkyl hydrogen phosphites useful are thosewherein the alkyl groups contain from 1 to 12 carbon atoms. These alkylgroups are, for example, methyl, ethyl, propyl, isopropyl, butyl,sec-butyl, t-butyl, hexyl, decyl, isodecyl, dodecyl and the like.

The following example serves to further illustrate the invention. Allparts are parts by weight unless otherwise expressly set forth.

EXAMPLE After stirring at 40 C. to dissolve the acid, the mixture iscooled to room temperature and filtered.

The lubrication of the composition is shown with a slow speed four ballmachine. A slow speed four ball machine measures the boundary lubricityaction of additives. This test is a variation of the well known ShellFour Ball Test in which a ball is rotated against three stationaryballs. Wear scars and/or seizure loads measure additive lubricity. Inthe slow speed instrument the three stationary balls are replaced withcircular discs. Standard operating conditions are:

3 kg. load 1 r.p.m. Room temperature to 700 The speed of rotation isvery low, namely one r.p.m. This equals 0.88 inch/minute. This is donefor two reasons. It insures boundary conditions, i.e., metal to metalcontact. It also eliminates metal skin temperature flashes which canoccur at high speeds. Thus the bulk oil temperature is equivalent to themetal surface temperature. Under these conditions wear is negligible andfriction is used to follow lubrication. After covering the ball and discwith the test oil, the initial friction is recorded. The test sample isthenheated at 700 F. with continuous recording of the friction. Thisgives a boundary frictiontemperature profile for the experimental fluidover this temperature range.

The polyphenyl ether composition of this example is tested by thisprocedure on 316 stainless steel. The measured coefficient of frictionremained below about 0.4 from room temperature to 700 F.

When the base fluid was tested under the same conditions the coefficientof friction showed a steep increase as the temperature was increased andexceeded 2.0 at 450 F. and remained between 1.0 and 2.0 through 700 F.

The embodiments in which an exclusive property or privilege is claimedare defined as follows:

1. Composition comprising a major amount of a polyphenyl ether and fromabout 0.01 to about 0.2% by weight of a perfluorodibasic aliphatic acidof the formula wherein n is an integer of from 1 to 6.

2. Composition of claim 1 wherein said perfluoro dibasic aliphtaic acidis present in amounts of from about 0.05 to about 0.1% by weight.

3. Composition of claim 1 wherein said per'fluoro dibasic aliphatic acidis perfluoroglutaric acid.

4. Composition of claim 2 wherein said perfluoro dibasic aliphatic acidis perfluoroglutaric acid.

5. A composition of claim 1 where n is from 1 to 3.

References Cited UNITED STATES PATENTS 3,409,677 ll/l968 Duncker et al.25252 R 3,476,815 11/1969 Williams et al. 25252 R 3,490,738 11/1970Stemnisk 25252 R 3,541,015 11/1970 Schultz et al 25252 R 3,567,7833/1971 Brown 25252 R 3,677,944 7/1972 Clark 25254.6

DANIEL E. WY-MAN, Primary Examiner Y. H. SMITH, Assistant Examiner US.Cl. X.R. 25252 R

